1. Field of the Invention
The present invention relates to an image reading apparatus which optically scans an original document to read an original image and a box used for making the image reading apparatus, and an image forming apparatus such as a copying machine comprising an image reading apparatus, facsimile machine comprising an image reading apparatus and the like and multifunctional machine produced by combining two or more of these.
2. Description of the Related Art
A typical example of image reading apparatuses which optically scan original documents to read the images of the original documents in use today is an image reading apparatus comprising a box and parts of the apparatus mounted on the box, the parts mounted on the box being at least a transparent table for supporting an original document, a first scanning unit which is disposed below the transparent table to illuminate the original document on the transparent table and reflect light reflected from the original document in an original document subscanning direction, a second scanning unit which reflects light reflected by the first scanning unit reversely in the subscanning direction, a drive mechanism which drives the first and second scanning units in the subscanning direction, a reading block having a photoelectric image pickup element and an optical system for leading reflected light coming from the second unit to the image pickup element to form an image, an image processor which processes image information from the image pickup element, and other components.
According to this type of image reading apparatus, the first and second scanning units are moved in the original document subscanning direction by the drive mechanism and simultaneously the original document mounted on the transparent plate for supporting an original document (normally a transparent glass plate) is optically scanned and light containing the image information reflected by the original document is led by the optical system in the reading block to the image pickup element having photoelectric conversion capability to form an image.
The image information read by the image pickup element is subjected to necessary processes by the image processor or other components, and is outputted from the image processor.
This type of imaging reading apparatuses which can be provided with an automatic document feeder sometimes also comprise a transparent plate for scanning a moving original document. In such an image reading apparatus, the original document can be fed out from an automatic document feeder while being passed over the transparent table, and the image of the document can be read by the first and second scanning units positioned in predetermined positions for reading the original document on the transparent plate for scanning a moving original document.
Such an image reading apparatus is used, for example, as a part of copying machines, and a part of multifunctional machines which combines the functions of a copying machine and a facsimile machine, or is used singly, for example, in such a manner that it is connected to a personal computer, or connected to a printer via a computer.
The image information outputted from the image processor is provided for formation of an copied image of the original document, transmission of the original image information to a recipient's facsimile machine, displaying of the image on an computer display, printing of the image by a printer, and for other purposes.
Size reduction and more compact designs are required for information appliances including image reading apparatuses today. Furthermore, universally designed image reading apparatuses which allow, for example, easy operation for physically handicapped people while being seated in wheelchairs are required.
Image reading apparatuses need to be improved and made thinner to fulfill these requests.
FIG. 8 shows a copying machine as an example. This copying machine D′ comprises an image forming portion B and an image reading apparatus A′ thereabove, and also comprises a plurality of cassettes C1 to C4 below the image forming portion B for containing recording mediums (for example, recording paper) with different sizes (A4 size, etc.) and an automatic document feeder ADF which is mounted on the image reading apparatus A′ and also serves as an openable and closable document cover. A tray portion T′ onto which a recording medium having an image formed thereon is discharged is formed between the image forming portion B and the image reading apparatus A′.
Taking this copying machine D′ as an example, one of the reasons why reduction of the thickness of the image reading apparatus A′ is required will be described.
The overall height H′ of the copying machine D′ is the sum of the height H2′ of the automatic document feeder ADF and the height H1′ of the image reading apparatus A′, image forming portion B and a portion CS including the cassettes C1-C4. The height of a recording medium discharge space above the tray portion T′ is H3′ in a portion thereof.
To meet the current demand for enhanced speed of image formation in copying machines of this type, that is, to increase the number of sheets of image formation per unit time, enhanced speed of image formation in the image forming portion B and of image reading in the image reading apparatus A′ must be of course achieved, but to make high-speed image formation more meaningful, it is also required to increase the recording medium capacity of the cassettes for accommodating recording mediums and increase the height H3′ of the recording medium discharge space above the tray portion T′. To meet such requirements, the height of the portion CS in which cassettes are placed needs to be increased to increase the recording medium capacity, and/or the height H3′ of the space needs to be increased to increase the capacity of recording mediums on which images are formed.
Such modifications, however, increase the overall size of the copying machine. In addition, a raise in the height positions of the image reading apparatus A′ and automatic document feeder ADF lowers their ease of operation, whereby the apparatus is no longer compliant with universal designs.
Therefore, in addition to increasing the recording medium capacities of the cassettes and increasing the height H3′ of the recording medium discharge space above the tray portion, in order to inhibit a raise in the height positions of the image reading apparatus A′ and automatic document feeder ADF or to lower their positions, the height Ha′ of the image reading apparatus A′ in the vertical direction must be low and the apparatus A′ must be made thinner.
Even in case where a recording medium discharge tray is not positioned between the image forming portion B and the image reading apparatus A′ but is provided in a protruding manner on the image forming portion B or a sorter or other components are additionally provided on the image forming portion B onto which recording mediums are discharged, increasing the height of the portion in which the cassettes are placed to increase the recording medium capacities of the cassettes in response to enhanced speed lowers the ease of operation because of the raise in the height positions of the image reading apparatus A′ and automatic document feeder ADF accordingly, whereby the apparatus is no longer compliant with universal designs.
Even when the image reading apparatus is used, for example, placed on a base such as a desk and connected to a computer, it is desirable that the image reading apparatus is made less bulky to facilitate installment and its height is reduced to comply with universal designs. A reduction in the thickness of the image reading apparatus is required also from such a perspective.
Regarding this point, for example, in Japanese Unexamined Patent Publication No. H11-69104, it is described that an image reading apparatus comprising a scanning means which moves approximately horizontally to scan an original document, an image reading means which carries out photoelectric conversion in response to the light reflected from the original document obtained by scanning by the scanning means, and an image processing means, an amplifier circuit, an A/D converter circuit, correction circuit and others which conducts a necessary processing on the image information from the image reading means, wherein part of the image processing means is positioned in a region above the lowermost end of the scanning means so as to avoid collision with the scanning means, and is positioned in a region below the optical path of the reflected light incident on the image reading means.
This publication describes that according to this image reading apparatus, the space necessary for the scanning means and image reading means and the space necessary for the image processing means overlap from the lowermost end of the scanning means to the optical path of the reflected light incident on the image reading means, whereby the thickness of the image reading apparatus can be reduced.
By the way, a box used for the image reading apparatus for mounting the scanning means and the like normally has a basic structure in which a base plate is attached to a rectangular frame, but sufficient strength of the box cannot be afforded only by such a basic structure. Therefore, it is recommended that a reinforcing member is arranged in and fixed to a box body having a structure in which a base plate is attached on a rectangular frame.
However, when such a reinforcing member is employed, a new measure will be necessary in correspondence with the employment of the reinforcing member to reduce the thickness of the image reading apparatus.
The image processing means described in Japanese Unexamined Patent Publication No. H11-69104 includes an A/D converter circuit which converts an analog signal received from the image reading means into a digital signal, but, in stead of the A/D converter circuit included in the image processing means, an A/D conversion board mounted on an additional circuit board may be possibly employed as the A/D converter circuit.
When such an A/D conversion board is employed, a new measure will be necessary in correspondence with the employment of the A/D conversion board to reduce the thickness of the image reading apparatus.
When the distance between the image pickup element and the image processor including the A/D converter circuit is too large, the distance between the image pickup element and the A/D conversion board is too large, or the distance between the A/D conversion board and the image processor not including the A/D converter circuit is too large, an electromagnetic noise which is a radio wave transmitted to the surroundings is generated, or contrarily the image signal is affected by an electromagnetic noise. This problem occurs especially noticeably in high-speed machines. To solve such problems, an expensive and bulky shielded line needs to be routed in the box, but reduced thickness of the image reading apparatus makes of the routing of the shielded line difficult.